Warm water from power plants counts as pollution too
Water pollution is not only oil slicks and chemical sludge. Power stations and factories that use rivers as coolant return the water warmer, and that heat alone can upset aquatic life. Changes in acidity, oxygen, salinity or cloudiness can all make water polluted without a single drop of poison.
One practical definition treats pollution as adding substances or forms of energy that change a body of water in ways that harm its legitimate uses. Water is usually judged polluted when human contamination makes it unfit for purposes such as drinking, or significantly changes its ability to support living communities like fish. It can affect lakes, rivers, oceans, reservoirs and groundwater alike.
Engineers distinguish point sources, with one identifiable origin such as a drain, a treatment plant or an oil spill, from non-point sources that are diffuse, like runoff from farmland. The four main origins are sewage, industry, agriculture and urban runoff, including stormwater. Damage builds up cumulatively over time, degrading ecosystems and spreading disease when contaminated water is used for drinking or irrigation.
Sewage carries a surprising cocktail. Besides nutrients and organic waste, it can hold chemicals from cosmetics and hygiene products, residues of hormones from livestock and human contraception, and synthetic compounds such as phthalates that mimic hormones, sometimes with effects at very low concentrations. Because hunting for disease-causing microbes directly is difficult and expensive, laboratories look instead for indicator organisms, typically coliform bacteria such as Escherichia coli, as a sign of faecal contamination. Microbes found in polluted surface water include Giardia, Cryptosporidium, Salmonella and norovirus.
Other threats come from petroleum fuels and lubricants washed off roads or spilled at sea, industrial solvents including PCBs and trichloroethylene, and PFAS, persistent compounds that linger in the environment. Heavy rain can overwhelm combined sewers and send untreated waste into rivers. Tackling all this takes infrastructure, management plans and laws, along with better sanitation, sewage and industrial wastewater treatment, erosion control and stormwater management.
Source: Water pollution
